feat(distribution): 分站可下调收号比例且不超过主站上限

让分销站能按自身能力下调收号比例扩大利润，同时把主站回收比例作为硬边界，避免分站把比例加得比主站更高。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/features/admin/views/AdminDistributionSitesView.vue

@@ -10,6 +10,7 @@ import {
   Clock,
   Picture,
   Upload,
+  Coin,
 } from '@element-plus/icons-vue'
 import {
   fetchDistributionSites,
@@ -45,6 +46,14 @@ const settlementForm = reactive({
   settlement_hold_days: defaultSettlementHoldDays.value,
 })
 
+const receiveRatioDialogVisible = ref(false)
+const receiveRatioSubmitting = ref(false)
+const receiveRatioForm = reactive({
+  site_id: 0,
+  site_name: '',
+  receive_ratio_delta: 0,
+})
+
 const qrDialogVisible = ref(false)
 const qrSubmitting = ref(false)
 const qrUploading = ref(false)
@@ -77,6 +86,29 @@ async function handleSettlementSubmit() {
   }
 }
 
+function handleOpenReceiveRatio(row: DistributionSite) {
+  receiveRatioForm.site_id = row.id
+  receiveRatioForm.site_name = row.site_name
+  receiveRatioForm.receive_ratio_delta = Number(row.receive_ratio_delta || 0)
+  receiveRatioDialogVisible.value = true
+}
+
+async function handleReceiveRatioSubmit() {
+  receiveRatioSubmitting.value = true
+  try {
+    await updateDistributionSite(receiveRatioForm.site_id, {
+      receive_ratio_delta: Number(receiveRatioForm.receive_ratio_delta),
+    })
+    ElMessage.success(`【${receiveRatioForm.site_name}】收号比例下调已更新`)
+    receiveRatioDialogVisible.value = false
+    await loadSites()
+  } catch (err) {
+    ElMessage.error(readError(err, '更新收号比例失败'))
+  } finally {
+    receiveRatioSubmitting.value = false
+  }
+}
+
 function handleOpenQrcode(row: DistributionSite) {
   qrForm.site_id = row.id
   qrForm.site_name = row.site_name
@@ -257,8 +289,8 @@ onMounted(() => {
       <div>
         <h2 class="page-title">分销站点管理</h2>
         <p class="page-subtitle">
-          开通分销站、配置结算冷却期与发布群固定二维码。利润按 35% 收号 / 40% 卖出 / 25%
-          服务费切分。
+          开通分销站、配置结算冷却期、收号比例上限与发布群固定二维码。利润按 35% 收号 / 40% 卖出 /
+          25% 服务费切分。
         </p>
       </div>
       <div class="header-actions">
@@ -314,6 +346,17 @@ onMounted(() => {
             </el-tag>
           </template>
         </el-table-column>
+        <el-table-column label="收号下调" width="110">
+          <template #default="{ row }">
+            <el-tag :type="Number(row.receive_ratio_delta || 0) > 0 ? 'warning' : 'info'" size="small">
+              {{
+                Number(row.receive_ratio_delta || 0) > 0
+                  ? `-${Number(row.receive_ratio_delta).toFixed(1)} 点`
+                  : '与主站一致'
+              }}
+            </el-tag>
+          </template>
+        </el-table-column>
         <el-table-column label="发布群二维码" width="120" align="center">
           <template #default="{ row }">
             <AuthImage
@@ -331,7 +374,7 @@ onMounted(() => {
             {{ formatDateTime(row.created_at) }}
           </template>
         </el-table-column>
-        <el-table-column label="操作" width="280" fixed="right">
+        <el-table-column label="操作" width="340" fixed="right">
           <template #default="{ row }">
             <el-button
               type="primary"
@@ -345,6 +388,9 @@ onMounted(() => {
             <el-button type="primary" link :icon="Clock" @click="handleOpenSettlement(row)">
               结算设置
             </el-button>
+            <el-button type="primary" link :icon="Coin" @click="handleOpenReceiveRatio(row)">
+              收号比例
+            </el-button>
             <el-button type="primary" link :icon="Picture" @click="handleOpenQrcode(row)">
               二维码
             </el-button>
@@ -522,6 +568,43 @@ onMounted(() => {
       </template>
     </el-dialog>
 
+    <!-- 分站收号比例（主站为上限） -->
+    <el-dialog
+      v-model="receiveRatioDialogVisible"
+      title="分站收号比例"
+      width="520px"
+      destroy-on-close
+    >
+      <el-alert
+        type="info"
+        :closable="false"
+        show-icon
+        title="主站回收比例是上限。下调点数越大，号主底价越高、分站利润空间越大，但不能高于主站比例。0 表示与主站一致。"
+        style="margin-bottom: 16px"
+      />
+      <el-form label-width="110px">
+        <el-form-item label="分销站点">
+          <el-input :model-value="receiveRatioForm.site_name" disabled />
+        </el-form-item>
+        <el-form-item label="相对主站下调">
+          <el-input-number
+            v-model="receiveRatioForm.receive_ratio_delta"
+            :min="0"
+            :max="20"
+            :step="0.1"
+            :precision="1"
+          />
+          <span class="settlement-hint">点（0-20）</span>
+        </el-form-item>
+      </el-form>
+      <template #footer>
+        <el-button @click="receiveRatioDialogVisible = false">取消</el-button>
+        <el-button type="primary" :loading="receiveRatioSubmitting" @click="handleReceiveRatioSubmit">
+          保存设置
+        </el-button>
+      </template>
+    </el-dialog>
+
     <!-- 发布群固定二维码 -->
     <el-dialog v-model="qrDialogVisible" title="发布群固定二维码" width="520px" destroy-on-close>
       <el-alert